Papers by Murugesan Rajaram
Journal of Immunology, May 1, 2010
Francisella tularensis contains four putative acid phosphatases that are conserved in Francisella... more Francisella tularensis contains four putative acid phosphatases that are conserved in Francisella novicida. An F. novicida quadruple mutant (AcpA, AcpB, AcpC, and Hap [DABCH]) is unable to escape the phagosome or survive in macrophages and is attenuated in the mouse model. We explored whether reduced survival of the DABCH mutant within phagocytes is related to the oxidative response by human neutrophils and macrophages. F. novicida and F. tularensis subspecies failed to stimulate reactive oxygen species production in the phagocytes, whereas the F. novicida DABCH strain stimulated a significant level of reactive oxygen species. The DABCH mutant, but not the wild-type strain, strongly colocalized with p47 phox and replicated in phagocytes only in the presence of an NADPH oxidase inhibitor or within macrophages isolated from p47 phox knockout mice. Finally, purified AcpA strongly dephosphorylated p47 phox and p40 phox , but not p67 phox , in vitro. Thus, Francisella acid phosphatases play a major role in intramacrophage survival and virulence by regulating the generation of the oxidative burst in human phagocytes.
BMC Biology, Nov 5, 2014
Background: Palmitoylation is a 16-carbon lipid post-translational modification that increases pr... more Background: Palmitoylation is a 16-carbon lipid post-translational modification that increases protein hydrophobicity. This form of protein fatty acylation is emerging as a critical regulatory modification for multiple aspects of cellular interactions and signaling. Despite recent advances in the development of chemical tools for the rapid identification and visualization of palmitoylated proteins, the palmitoyl proteome has not been fully defined. Here we sought to identify and compare the palmitoylated proteins in murine fibroblasts and dendritic cells. Results: A total of 563 putative palmitoylation substrates were identified, more than 200 of which have not been previously suggested to be palmitoylated in past proteomic studies. Here we validate the palmitoylation of several new proteins including Toll-like receptors (TLRs) 2, 5 and 10, CD80, CD86, and NEDD4. Palmitoylation of TLR2, which was uniquely identified in dendritic cells, was mapped to a transmembrane domain-proximal cysteine. Inhibition of TLR2 S-palmitoylation pharmacologically or by cysteine mutagenesis led to decreased cell surface expression and a decreased inflammatory response to microbial ligands. Conclusions: This work identifies many fatty acylated proteins involved in fundamental cellular processes as well as cell type-specific functions, highlighting the value of examining the palmitoyl proteomes of multiple cell types. Spalmitoylation of TLR2 is a previously unknown immunoregulatory mechanism that represents an entirely novel avenue for modulation of TLR2 inflammatory activity.
Cells, Dec 31, 2020
The immune system plays a pivotal role in the initiation, development and resolution of inflammat... more The immune system plays a pivotal role in the initiation, development and resolution of inflammation following insult or damage to organs. The heart is a vital organ which supplies nutrients and oxygen to all parts of the body. Heart failure (HF) has been conventionally described as a disease associated with cardiac tissue damage caused by systemic inflammation, arrhythmia and conduction defects. Cardiac inflammation and subsequent tissue damage is orchestrated by the infiltration and activation of various immune cells including neutrophils, monocytes, macrophages, eosinophils, mast cells, natural killer cells, and T and B cells into the myocardium. After tissue injury, monocytes and tissue-resident macrophages undergo marked phenotypic and functional changes, and function as key regulators of tissue repair, regeneration and fibrosis. Disturbance in resident macrophage functions such as uncontrolled production of inflammatory cytokines, growth factors and inefficient generation of an anti-inflammatory response or unsuccessful communication between macrophages and epithelial and endothelial cells and fibroblasts can lead to aberrant repair, persistent injury, and HF. Therefore, in this review, we discuss the role of cardiac macrophages on cardiac inflammation, tissue repair, regeneration and fibrosis.
Age, Mar 3, 2014
As we age, there is an increased risk for the development of pulmonary diseases, including infect... more As we age, there is an increased risk for the development of pulmonary diseases, including infections, but few studies have considered changes in lung surfactant and components of the innate immune system as contributing factors to the increased susceptibility of the elderly to succumb to infections. We and others have demonstrated that human alveolar lining fluid (ALF) components, such as surfactant protein (SP)-A, SP-D, complement protein C3, and alveolar hydrolases, play a significant innate immune role in controlling microbial infections. However, there is a lack of information regarding the effect of increasing age on the level and function of ALF components in the lung. Here we addressed this gap in knowledge by determining the levels of ALF components in the aging lung that are important in controlling infection. Our findings demonstrate that pro-inflammatory cytokines, surfactant proteins and lipids, and complement components are significantly altered in the aged lung in both mice and humans. Further, we show that the aging lung is a relatively oxidized environment. Our study provides new information on how the pulmonary environment in old age can potentially modify mucosal immune responses, thereby impacting pulmonary infections and other pulmonary diseases in the elderly population.
Frontiers in Immunology, Jan 24, 2017
We crafted human immunodeficiency virus (HIV)-like particles of diameter about 140 nm, which expr... more We crafted human immunodeficiency virus (HIV)-like particles of diameter about 140 nm, which expressed two major HIV-1 proteins, namely, env and gag gene products, and used this reagent to simulate the rate of decay of HIV from the blood stream of BALB/c male mice. We found that most (~90%) of the particles were eliminated (cleared) from the blood by the liver sinusoidal endothelial cells (LSECs), the remainder from Kupffer cells; suggesting that LSECs are the major liver scavengers for HIV clearance from blood. Decay was rapid with kinetics suggesting second order with respect to particles, which infers dimerization of a putative receptor on LSEC. The number of HIV-like particles required for saturating the clearance mechanism was approximated. The capacity for elimination of blood-borne HIV-like particles by the sinusoid was 112 million particles per minute. Assuming that the sinusoid endothelial cells were about the size of glassadherent macrophages, then elimination capacity was more than 540 particles per hour per endothelial cell.
Research Square (Research Square), Jul 28, 2022
Pseudomonas aeruginosa (P.a.) infection accounts nearly 20% of all cases of hospital acquired pne... more Pseudomonas aeruginosa (P.a.) infection accounts nearly 20% of all cases of hospital acquired pneumonia with mortality rates > 30%. P.a. infection induces a robust in ammatory response, which ideally enhances bacterial clearance. Unfortunately, excessive in ammation can also have negative effects, and often leads to cardiac dysfunction with associated morbidity and mortality. However, it remains unclear how P.a. lung infection causes cardiac dysfunction. Using a murine pneumonia model, we found that of P.a. infection of lungs led to severe cardiac left ventricular dysfunction and electrical abnormalities. More speci cally, we found that neutrophil recruitment and release of S100A8/A9 in the lungs activates the TLR4/RAGE signaling pathways, which in turn enhance systemic in ammation and subsequent cardiac dysfunction. Paradoxically, global deletion of S100A8/A9 did not improve but aggravated cardiac dysfunction and immortality likely due to uncontrolled bacterial burden in the lungs and heart. Our results indicate that P.a. infection induced release of S100A8/9 is double-edged, providing increased risk for cardiac dysfunction yet limiting P.a. growth.
The Journal of Immunology
Pneumonia in ICU patients carries a bleak prognosis with high risk for cardiac dysfunction, large... more Pneumonia in ICU patients carries a bleak prognosis with high risk for cardiac dysfunction, largely due to cardiac infection and inflammation. Pseudomonas aeruginosa (P.a.) infection accounts nearly 20% of all cases of hospital acquired pneumonia with mortality rates >30%. P.a. infection induces a robust inflammatory response, which ideally enhances bacterial clearance. Unfortunately, excessive inflammation can also have negative effects, and often leads to cardiac dysfunction with associated morbidity and mortality. However, it remains unclear how P.a. lung infection causes cardiac dysfunction. Using a murine pneumonia model, we found that of P.a. infection of lungs led to severe cardiac left ventricular dysfunction and electrical abnormalities. More specifically, we found that neutrophil recruitment and release of S100A8/A9 in the lungs activates the TLR4/RAGE signaling pathways, which in turn enhance systemic inflammation and subsequent cardiac dysfunction. Paradoxically, glob...
The Journal of Immunology
Influenza A virus (IAV) and SARS-CoV-2 are both acute respiratory viruses currently circulating i... more Influenza A virus (IAV) and SARS-CoV-2 are both acute respiratory viruses currently circulating in the human population. Prior IAV infection enhances SARS-CoV-2 infectivity and lung pathogenesis in mice; however, underlying mechanisms and the extent that co-infection leads to involvement of other organs in disease severity remains unknown. Herein, we investigated the impact of prior IAV infection on SARS-CoV-2 pathogenesis and cardiomyocyte function. IAV infection induces the expression of ACE2 in human lung epithelial cells, lung fibroblasts, macrophages, cardiac fibroblasts (HCFs), and hiPSC-Cardiomyocytes (CMs). Interestingly, we detected poorly glycosylated ACE2 in lung epithelial cells and cardiac fibroblasts. In contrast, expression of a heavily glycosylated form of ACE2 is induced by IAV in CMs. In all cell types, IAV infection enhances SARS-CoV-2 viral entry. However, efficient SARS-CoV-2 replication was uniquely inhibited in CMs. Glycosylation of ACE2 correlated with enzyma...
The Journal of Immunology
Mycobacterium avium complex (MAC) consists of M. avium and M. intracellulare and enters the host ... more Mycobacterium avium complex (MAC) consists of M. avium and M. intracellulare and enters the host primarily through the gastrointestinal track and pulmonary route. MAC is a common cause of mycobacterial infection in immune compromised individuals including, the elderly and those with COPD, HIV/AIDS or cystic fibrosis. The disease symptoms are reminiscent of tuberculosis (TB). Mycobacterium can infect every organ in the body including the heart causing carditis (pericarditis, myocarditis and endocarditis). Myocardial TB is difficult to diagnose and treat and can cause heart failure and ventricular tachyarrhythmia which can ultimately lead to sudden cardiac arrest. Very little is known regarding cardiac dysfunction during mycobacterial infection in the elderly. In this study we examined cardiac electrical activity, cardiac inflammation and fibrosis in young and old mice after 32 days of M. avium infection. The electrocardiogram of old mice shows abnormalities that include sinus node pa...
The Journal of Immunology
As the number of elderly individuals increases, infectious diseases, such as influenza, pneumonia... more As the number of elderly individuals increases, infectious diseases, such as influenza, pneumonia and tuberculosis have become a significant public health concern. Recent interest in pathogen recognition via toll-like receptors (TLR) and the ability of TLR agonists to generate enhanced vaccine immunogenicity has led to questions regarding altered immune function in the elderly. In contrast to young mice, recent studies in our lab have shown that in old mice, Mycobacterium tuberculosis infected pulmonary macrophages can utilize a TLR2 independent pathway to generate cytokine secretion. This new development of specific altered TLR function in the elderly requires more analysis before vaccines can be generated to increase protective immunity. In this study, we will elucidate the differences in cytokine profile in the presence and absence of TLR2 by siRNA knockdown in old mice. This will allow us to determine changes that impair protection against infectious disease in old age. We will ...
Pseudomonas aeruginosa (P.a.) infection accounts nearly 20% of all cases of hospital acquired pne... more Pseudomonas aeruginosa (P.a.) infection accounts nearly 20% of all cases of hospital acquired pneumonia with mortality rates > 30%. P.a. infection induces a robust inflammatory response, which ideally enhances bacterial clearance. Unfortunately, excessive inflammation can also have negative effects, and often leads to cardiac dysfunction with associated morbidity and mortality. However, it remains unclear how P.a. lung infection causes cardiac dysfunction. Using a murine pneumonia model, we found that of P.a. infection of lungs led to severe cardiac left ventricular dysfunction and electrical abnormalities. More specifically, we found that neutrophil recruitment and release of S100A8/A9 in the lungs activates the TLR4/RAGE signaling pathways, which in turn enhance systemic inflammation and subsequent cardiac dysfunction. Paradoxically, global deletion of S100A8/A9 did not improve but aggravated cardiac dysfunction and immortality likely due to uncontrolled bacterial burden in the...
The Journal of Immunology, 2021
Neutralizing Abs suppress HIV infection by accelerating viral clearance from blood circulation in... more Neutralizing Abs suppress HIV infection by accelerating viral clearance from blood circulation in addition to neutralization. The elimination mechanism is largely unknown. We determined that human liver sinusoidal endothelial cells (LSEC) express FcγRIIb as the lone Fcγ receptor, and using humanized FcγRIIb mouse, we found that Ab-opsonized HIV pseudoviruses were cleared considerably faster from circulation than HIV by LSEC FcγRIIb. Compared with humanized FcγRIIb-expressing mice, HIV clearance was significantly slower in FcγRIIb knockout mice. Interestingly, a pentamix of neutralizing Abs cleared HIV faster compared with hyperimmune anti-HIV Ig (HIVIG), although the HIV Ab/Ag ratio was higher in immune complexes made of HIVIG and HIV than pentamix and HIV. The effector mechanism of LSEC FcγRIIb was identified to be endocytosis. Once endocytosed, both Ab-opsonized HIV pseudoviruses and HIV localized to lysosomes. This suggests that clearance of HIV, endocytosis, and lysosomal traffi...
Cardiac dysfunction is a common extrapulmonary complication of severe influenza virus infection. ... more Cardiac dysfunction is a common extrapulmonary complication of severe influenza virus infection. Prevailing models propose that influenza-associated heart dysfunction is indirectly triggered by cytokine mediated cardiotoxicity downstream of the inflamed lung, rather than by direct infection of cardiac tissue. To test the etiology of cardiac dysfunction resulting from influenza virus infection, we generated a novel recombinant H1N1 influenza A virus that was attenuated in cardiomyocytes by incorporation of target sequences for miRNAs expressed specifically in that cell type (miR133b and miR206). Compared with control virus, mice infected with the miR-targeted virus had significantly reduced heart viral titers, confirming cardiac attenuation of viral replication. The miR-targeted virus, however, was fully replicative and inflammatory in lungs when compared to control virus, and induced similar systemic weight loss. The miR-targeted virus induced considerably lower levels of cardiac ar...
SSRN Electronic Journal, 2021
Lipopolysaccharides (LPSs) cause lethal endotoxemia if not rapidly cleared from blood circulation... more Lipopolysaccharides (LPSs) cause lethal endotoxemia if not rapidly cleared from blood circulation. Liver sinusoidal endothelial cells (LSEC) systemically clear LPS by unknown mechanisms. We discovered that LPS clearance through LSEC involves endocytosis and lysosomal inactivation via Stabilin-1 and 2 (Stab1 and Stab2) but does not involve TLR4. Cytokine production was inversely related to clearance/endocytosis of LPS by LSEC. When exposed to LPS, Stabilin double knockout mice (Stab DK) and Stab1 KO, but not Stab2 KO, showed significantly enhanced systemic inflammatory cytokine production and early death compared with WT mice. Stab1 KO is not significantly different from Stab DK in circulatory LPS clearance, LPS uptake and endocytosis by LSEC, and cytokine production. These data indicate that (1) Stab1 receptor primarily facilitates the proactive clearance of LPS and limits TLR4-mediated inflammation and (2) TLR4 and Stab1 are functionally opposing LPS receptors. These findings suggest that endotoxemia can be controlled by optimizing LPS clearance by Stab1.
Aging Cell, 2019
Biological aging dynamically alters normal immune and cardiac function, favoring the production o... more Biological aging dynamically alters normal immune and cardiac function, favoring the production of pro‐inflammatory cytokines (IL‐1β, IL‐6, and TNF‐α) and increased instances of cardiac distress. Cardiac failure is the primary reason for hospitalization of the elderly (65+ years). The elderly are also increasingly susceptible to developing chronic bacterial infections due to aging associated immune abnormalities. Since bacterial infections compound the rates of cardiac failure in the elderly, and this phenomenon is not entirely understood, the interplay between the immune system and cardiovascular function in the elderly is of great interest. Using Mycobacterium avium, an opportunistic pathogen, we investigated the effect of mycobacteria on cardiac function in aged mice. Young (2–3 months) and old (18–20 months) C57BL/6 mice were intranasally infected with M. avium strain 104, and we compared the bacterial burden, immune status, cardiac electrical activity, pathology, and function o...
Influenza virus primarily targets the lungs, but dissemination and damage to heart tissue is also... more Influenza virus primarily targets the lungs, but dissemination and damage to heart tissue is also known to occur in severe infections. Despite this knowledge, influenza virus-induced cardiac pathogenesis and its underlying mechanisms have been difficult to study due to a lack of small animal models. In humans, polymorphisms in the gene encoding interferon-induced transmembrane protein 3 (IFITM3), an antiviral restriction factor, are associated with susceptibility to severe influenza, but whether IFITM3 deficiencies contribute to other aspects of pathogenesis, including cardiac dysfunction, is unknown. We now show that IFITM3 deficiency in a newly generated knockout (KO) mouse model exacerbates illness and mortality following influenza A virus infection. Enhanced pathogenesis correlated with increased replication of virus in the lungs, spleens, and hearts of KO mice relative to wildtype (WT) mice. IFITM3 KO mice exhibited normal cardiac function at baseline, but developed severely ab...
JACC: Basic to Translational Science, 2018
The pathogenesis of human heart failure is complex, and the creation of new therapeutic strategie... more The pathogenesis of human heart failure is complex, and the creation of new therapeutic strategies for human heart failure is critical. Identifying the molecular pathways underlying heart failure is important to define potential new therapeutic targets.
mBio, Jan 2, 2018
The ability to grow at mammalian body temperatures is critical for pathogen infection of humans. ... more The ability to grow at mammalian body temperatures is critical for pathogen infection of humans. For the thermally dimorphic fungal pathogen Histoplasma capsulatum, elevated temperature is required for differentiation of mycelia or conidia into yeast cells, a step critical for invasion and replication within phagocytic immune cells. Posttranslational glycosylation of extracellular proteins characterizes factors produced by the pathogenic yeast cells but not those of avirulent mycelia, correlating glycosylation with infection. Histoplasma yeast cells lacking the Pmt1 and Pmt2 protein mannosyltransferases, which catalyze O-linked mannosylation of proteins, are severely attenuated during infection of mammalian hosts. Cells lacking Pmt2 have altered surface characteristics that increase recognition of yeast cells by the macrophage mannose receptor and reduce recognition by the β-glucan receptor Dectin-1. Despite these changes, yeast cells lacking these factors still associate with and s...
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Papers by Murugesan Rajaram